Resources from a subterranean reservoir (e.g., oil) may be removed from the reservoir by injecting a working fluid into the reservoir. For example, carbon dioxide-based tertiary oil recovery has become a popular recovery process. This type of recovery involves injecting carbon dioxide (CO2) into a subterranean reservoir to recover oil from the reservoir. Significant volumes of CO2 can be used to extract the oil. Given the volumes of the CO2 that are required to be injected into the reservoir, this type of recovery often occurs in an environment where CO2 is a highly constrained and a supply-limited commodity. This can require operators to make the best possible use of the instantaneous CO2 that is available in the market.
Effective use of CO2 for enhanced tertiary oil recovery (CO2EOR) involves various alternative methods, such as the water-alternating-gas (WAG) method. The WAG method involves periodically alternating the injection of CO2 and water into the reservoir according to a schedule with the intent of sweeping the leftover oil out of the reservoir. Effective use of WAG requires meeting multiple constraints while seeking to increase the rate of oil extraction. Inappropriately designed WAG schedules can result in poor production and early breakthrough of water and/or gas, thereby making the recovery of oil viable only for short periods of time. Presently, WAG schedules are based on knowledge of the reservoir and prior experience with other reservoirs and require a significant amount of time to develop.